Parasitic diatoms inside antarctic sponges

Antarctic sponges may host large populations of planktonic and benthic diat oms. After settling on the sponge, these diatoms enter its body through pin acocytes (1) and form, there, large mono- or pauci-specific assemblages. Ye t the total amount of carbohydrates in the invaded sponge tissue is inverse ly correlated with that of chlorophyll-a. We suggest, therefore, that endob iont diatoms utilize the products of the metabolism of their host as an ene rgy source. This is the first evidence indicating that an endobiotic autotr ophic organism may parasitize its animal host. Moreover, this unusual symbi otic behavior could be a successful strategy that allows the diatom to surv ive in darkness.